Drive chains for bicycles with a derailleur system are composed of chain links which are arranged so as to be able to he pivoted with respect to each other and by means of which a closed chain loop is formed for drive force transmission. These chain links can be rotated relative to each other about chain pins, wherein the chain pins are received by holes which are located centrally in the two round end regions of each chain plate. The two end regions of each chain plate are connected to each other by means of a connection region with an outer contour which is in most cases constructed in a tapered manner. The chain links have either a pair of inner plates or a pair of outer plates. The inner plates have at their inner side collars, wherein a chain roller is rotatably arranged on a pair of collars which are arranged in a mirror-symmetrical manner relative to each other, respectively. The teeth of the chain wheels can engage in the intermediate spaces between the plate pairs.
This engagement operation takes place both in the case of a driving operation, in which the chain moves into engagement with teeth on a single chain wheel, and when the chain is displaced when switching from one chain wheel to the adjacent chain wheel. In order to carry out these engagement functions, it is desirable to construct the intermediate spaces between the plate pairs to be as large as possible in the direction perpendicular to the inner side of the plates. On the inner plates which are located more closely relative to each other, chamfers help to form an introduction funnel-like member for the teeth of the chain wheel being introduced into the intermediate spaces.
In the development of derailleur systems for bicycles which comprise a front chain wheel, roller chain, multiple rear sprockets and associated shifting devices, the number of sprockets on the multiple sprocket arrangement has continuously increased in a gradual manner. This has involved changes of the dimensions of sprockets, chain plates, chain pins and chain rollers, primarily the dimensions in the direction parallel to the longitudinal axis of the chain pins. Consequently, the chain is adapted to the rear sprockets which are positioned on the rear wheel hub with increasingly small axial spacing with respect to each other. In this instance, it is clear that the components of the chain which protrude in an axial direction beyond the outer side of the chain are also obstructive since they can come into contact with components of the adjacent sprocket in an undesirable and disruptive manner.
A reduction of the dimensions of the components of the chain leads in this instance to an increase of the loads for the chain, for example, the surface pressure on the chain pins which have become shorter. This results in an increase of the wear which is counteracted, for example, with the use of harder materials or by the provision of a more wear-resistant surface coating or by means of hardening of the surface.
The single-sided increase of the surface hardness of the chain components in the chain/chain wheel system at the side of the chain alone leads in this instance to a more rapid wear at the side of the chain wheels or the sprockets.
EP 1 522 490 A2 sets out chamfers in the direction towards the outer contour of the plates which arc intended to reduce the generation of noise when the sprocket teeth leave the intermediate plate spaces. It is described that noise is produced when the tooth tip or an edge on the tooth tip slides over edges on the outer contour of the chain plates. This sliding takes place when the chain plate and sprocket tooth move out of engagement during normal driving operation without any gear change with the chain which extends in an oblique manner away from the multiple sprocket assembly and also during gear change operation when the change portion of the chain which extends from one chain wheel to the adjacent chain wheel moves in a radially outward direction away from the tooth arrangement. This takes place when the change portion of the chain is moved in from the rear sprocket into the tensioned strand of the chain and when the change portion of the chain is moved from the front chain wheel into the slack strand of the chain.
This approach for reducing noise has also been implemented in the structural solutions which are set out in DE 10 2014 215 928 and in DE 10 2014 215 960.
The patent application U.S. Pat. No. 4,642,078 sets out a drive chain which is constructed in a particularly narrow manner and which is suitable for a multiple sprocket assembly on a rear wheel hub with a high number of gears. The drive chain set out has protruding inner plates and planar outer plates.
The inner side of the connection region of the inner plates has in comparison with the contact face between the chain roller and inner side of the inner plate an offset in outward direction which, when the material thickness of the inner plate is retained, also appears on the outer side on the connection region of the inner plates. Starting from the outer contour of the connection region of the inner plates, there is an outward protuberance which forms a funnel-like opening for the introduction of the teeth of the sprocket or chain wheel. The clear width between the plates of the inner plate pair is on the whole increased by the offset mentioned. Consequently, favorable conditions have been provided for the introduction of a tooth into the inner plate intermediate space.
In EP 2 535 616 the solution from U.S. Pat. No. 4,642,078 has been developed by the outer side on the connection region of the inner plate being constructed in a planar manner. There is consequently produced at the connection region of the inner plate a smaller material thickness in comparison with the round end regions of the inner plate. A reduced material thickness at the connection region of the inner plate has also already been implemented in DE 197 05 018.
With multiple sprocket assemblies having a further increased the number of sprockets, it is consequently necessary to take measures to obtain or achieve a reliable engagement of the sprocket teeth in the intermediate space between a pair of inner plates. These measures include the reduction of the dimensions, for example, a shortening of the length of chain pins and chain rollers which leads to an increase of the component loads and to increased wear.